Temperatures in the 20s and 30s are in the forecast again beginning at 10 p.m. Thursday and continuing through 8 a.m. Friday for the coastal and valley areas of San Diego County.
The National Weather Service says sensitive outdoor plants may be killed if left uncovered.
The frosty weather has caused some San Diego County growers to protect their crops.
"It's mostly the growers in low-lying areas because where the cold air will descend and then sit there," said Eric Larson, executive director of the San Diego County Farm Bureau. "And so if growers in the bottoms of valleys or in little pockets of low-lying land, those are the folks at risk."
Larson said citrus crops are typically grown in those areas because they tend to be more tolerant to cold temperatures. He also said nursery plants are at risk too.
"Nurseries are getting their plants ready for late-winter and spring sales so there could be some soft-growing tips on the nursery plants and those can be damaged by the cold," said Larson.
To protect their crops, Larson said some farmers will use large wind machines to mix warmer air with the cold air while others use water over the tops of plants He said the ice formed gives off heat, protecting the plants.
"The farmers are doing fine, there's been no cold so far that would really damage the crops, maybe just a little nick here and there but nothing of great concern," said Larson.
He said the current temperatures and conditions are nothing like the county's multibillion dollar agriculture industry faced in 2007 when a prolonged freeze cost farmers $50 million in damage.
